Miredo runs on GNU/Linux kernel and some other platforms and it's FREE software.

The purpose of Teredo IPv6 tunneling is to provide IPv6 connectivity to users behind NAT devices, most of which do not support IPv6, and not even Proto-41 forwarding.

For this to work, users need to have a Teredo client running on their system, such as Miredo, or the updated IPv6 stack from Microsoft Windows XP Service Pack 2 (that was previously provided in Microsoft's Advanced Networking pack).